Encoding an optical video disc to inhibit video tape recording

ABSTRACT

A system and method for encoding an optional video disc to inhibit unauthorized recording of played back signals by conventional videotape recorders is provided. A source program is mounted on a video signal generating means. The video signal is modified by increasing and decreasing time durations from a standard horizontal line duration of pre-established maximums and minimums. The modified video signal is recorded on a previously blank optical video disc.

The present invention is related to co-pending application Ser. No.180,369, filed Apr. 11, 1988 which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to optical video discs and, more particularly, toa method and apparatus for encoding an optical video disc to inhibitvideo tape recording.

BACKGROUND OF THE INVENTION

Optical video discs provide a means of distributing movies and otherprogramming in a pre-recorded format for on-demand viewing on atelevision receiver. When played on a suitable device, a video discproduces a standard television signal (NTSC, PAL, etc.) which can bedisplayed on a television receiver or monitor. This signal can also berecorded on any standard video tape recorder (VHS, Beta, 3/4 inch,U-Matic, etc.). As such, copies of any pre-recorded program can beeasily and inexpensively made.

With the vast number of video tape recorders (VTR's) now in use, it hasbecome commonplace for users to record off-the-air television programsfor subsequent and repeated viewing. In addition, consumers haveenthusiastically embraced pre-recorded video programming, typicallycommercially successful motion pictures; and this has resulted in largelibraries of pre-recorded video tapes for sale or rent to the public.The profit associated with selling o renting these pre-recorded videotapes has spawned large scale video tape piracy. Such "pirates"reproduce hundreds or thousands of unauthorized copies of a singlepre-recorded program on video tape. This deprives the rightful owners ordistributors of the programs of their lawful income. Since currently,the programs on optical video discs are freely recordable by VTR's thisrepresents an easy source for pirates.

Optical video discs are manufactured by molding a plastic material in apress, much as standard phonograph records are made. Signal informationis put on the disc in a spiral pattern analogous to the spiral groove ofa phonograph record in the form of tiny pits. The pits form arepresentation of a frequency. This frequency is modulated by the videosignal and, by using an FM detector in the player, the original videosignal is recovered.

Optical video discs are made in two formats: "constant angularvelocity"; and "constant linear velocity". In the first case theturntable motor operates at constant speed such that the linear velocitybetween the information path and the transducer is greatest at theoutside of the disc and gradually decreases as playback proceeds alongthe spiral towards the center of the disc. In the second case theturntable motor speed varies with the radial position of the transducer,such that a constant linear velocity is maintained between theinformation path and the transducer. This requires the turntable speedto steadily increase as playback proceeds along the spiral path towardsthe center of the disc. The methods of the present invention can beapplied to both formats.

SUMMARY OF THE INVENTION

Broadly, the apparatus disclosed in co-pending application Ser. No.180,369 processes a conventional video signal, such as an NTSCtelevision signal, such that a video picture may be derived anddisplayed therefrom by a conventional television receiver withoutadditional decoding, decryption, or further processing, yet aconventional video recorder is prevented from recording and playing backthat processed video signal. This copy prevention is achieved byincreasing and decreasing the length of respective field or frameintervals above and below their conventional lengths. Althoughconventional television receivers can "follow" such variable framelengths, conventional video recorders cannot. For example, aconventional frame in the NTSC standard is formed of 525 horizontal lineintervals. In accordance with the aforementioned patent application, theframe length is increased by adding more line intervals thereto and isdecreased by providing less than the standard 525 lines. Alternatively,the frame length of a 525-line frame may be increased by enlarging thetime durations of at least some line intervals above the standard 63.5microseconds duration and decreased by reducing the line durations belowthis standard. The rate at which the frame length increases anddecreases, the maximum and minimum lengths or durations of a frame andthe number of frames which remain at the maximum and minimum lengthsconstitute what is referred to in the aforementioned patent applicationas a "profile." The profile determines frame lengths and varies fromtime-to-time.

Notwithstanding such changes in the video frame lengths as well aschanges in the profiles which control those lengths, conventionaltelevision receivers are capable of detecting the vertical synchronizingsignals included in each video field and, thus, produce accurate videopictures from those video signals without undesired pictureinterference. However, the usual servo control systems included invirtually every video tape recorder (VTR) are unable to "lock" onto thevertical synchronizing signals which occur at increasing and decreasingperiods in the processed video signal. Thus, whereas accurate videopictures are reproduced by conventional television receivers, the videosignals which are processed with varying profiles, as disclosed in theaforementioned patent application, are not accurately recorded andreproduced by conventional VTRs.

The present invention incorporates a method and apparatus described insaid co-pending application and uses it for the preparation andmanufacture of optical video discs.

Molds used to mass manufacture optical video discs are made from amaster disc. A master disc is prepared by placing a blank disc on aturntable. Mounted above the turntable is a laser; and optics focus thelaser to a spot on the disc. A transport, controlled by a transportdriver moves the laser radially inwardly toward the center of the disc.

A source program, to be mastered, is generally in the form of a highquality video tape. The video tape is played on an appropriate playbackunit which provides video, audio and time code output signals. Thesesignals, along with a predetermined profile are fed into a videomodification processor constructed in accordance with said co-pendingapplication.

Video and audio signals are output from the video modification processorto a signal processor. The signal processor configures the signals forrecording appropriate to standards and characteristics established foroptical video discs. The output from the signal processor is then fedthrough a frequency modulator to frequency modulate a carrier whichforms the signal to be recorded. A laser driver amplifies the signal andmatches its characteristics to those of the laser.

The resulting master disc is used to create molds for the manufacture ofadditional optical video discs. On playback, replicates made from themaster provide a modified signal such that the program can be displayedon a television monitor but cannot be recorded on a conventional videotape recorder.

OBJECT OF THE INVENTION

Accordingly, it is an object of the present invention to provide amethod and apparatus for making an optical video disc which, when playedback on a standard player, will produce a video output signal which canbe displayed on a standard television receiver or monitor but whichcannot be recorded on a standard video tape recorder, thus making itimpossible to make unauthorized copies easily and inexpensively.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic representation of a typical system for producingan optical video disc master; and

FIG. 2 is a schematic representation of a system for producing anoptical video disc master in accordance with the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The molds which are used to manufacture optical video discs are madefrom a master disc on which the video material is recorded, either inreal time or slowed down from real time. It is during this recordingprocess that the methods of the present invention are employed to modifythe recorded signal such that tap copies cannot be made from thefinished optical disc. The methods of the present invention can beapplied both with real time and slowed-down recording, but, forsimplicity, will be described only for real time recording.

FIG. 1 shows a typical system for producing an optical video discmaster. A blank disc 13, which will become the master, is placed on aturntable 10. A motor driven with a signal supplied by motor driver 12causes the turntable to rotate at either a constant speed or, inaccordance with another embodiment, at a regularly increasing speeddepending on the frequency of a signal 61 supplied by a controller 60.For constant speed the frequency of signal 61 exhibits, for example, aconstant 30Hz (for NTSC) producing a turntable speed of 1800 rpm. Forconstant linear velocity recording, the frequency of signal 61 starts,for example, at about 10Hz and steadily increases to 30Hz producing aturntable speed that increases from 600 rpm to 1800 rpm. Motor 11 ispreferably a synchronous motor driven by an AC signal; however, a DCmotor may be used with an appropriate serv to synchronize its speed withthe signal 61 from the controller 60.

Mounted above the turntable 10 is a laser 20. Optics 21 focus the laserto a spot 22 on the disc 13 on turntable 10. The laser 20 (or at least aportion of its optics) is mounted on a transport 23 which moves spot 22radially from the outer perimeter of the disc 13 towards the center asthe recording process proceeds. Transport 23 is controlled by atransport driver 24 in response to signals 62 from controller 60.Although a laser is shown, other techniques, including electron beamsand mechanical styli, may be used to produce the usual pits in the disc13. A servo system may also be included with the optics 21 toautomatically maintain the focus of spot 22 as the disc 13 rotates andthe transport 23 moves the laser 20.

The program (video and accompanying audio) to be mastered is generallysupplied in the form of broadcast quality video tape, such as in the 1inch, type `C`, format. The program tape (not shown) is mounted on VTR40 and played to provide a signal to be recorded on the master videodisc. If the source material is supplied in another format, VTR 40 isprovided with a format compatible with the source material. Duringplayback, VTR 40 is synchronized to a master sync generator 50 by a syncsignal 51 supplied to the VTR. It is assumed that VTR 40 includes theusual time base corrector so that the output is a standard video signalwith a stable time base locked to master sync generator 50.

The video and audio outputs, 41 and 42 respectively of VTR 40, arenormal baseband video (NTSC, PAL, etc.) and baseband audio (mono orstereo) signals. These outputs 41 and 42 are supplied to an electronicspackage 30 comprising a signal processor 31, a frequency modulator 32and a laser driver 33. Signal processor 31 conditions the video signal41 for recording as appropriate to the characteristics and standardsestablished for optical video discs (e.g. the standards andcharacteristics which govern the operation of a Pioneer® video discplayer). Such characteristics and standards include peak-limiting,preemphasis, etc. Signal processor 31 also processes the audio signals42 by modulating them on subcarriers. The output signal from signalprocessor 31 is used by frequency modulator 32 to frequency modulate acarrier which forms the signal to be recorded on the disc 13. Laserdriver 33 amplifies this signal and matches its characteristics to thoseof laser 20.

In practice, a master is made by initially mounting a blank disc 13 onturntable 10 (motor 11 is at a standstill). A source video tape ismounted on VTR 40 and the transport 23 is positioned in the vicinity ofthe outer edge of the blank disc 13. A motor start input 63 tocontroller 60 is then activated to supply signal 61 to motor driver 12.Depending on input 65, the frequency of signal 61 is at, for example, at10Hz if constant linear velocity is selected; or at, for example, 30Hzif constant angular velocity is selected. The VTR 40 is started next.When an initial cue point is reached, a transport start input 64 tocontroller 60 is activated to begin the recording process. If input 65is set to constant linear velocity, the controller 60 graduallyincreases the frequency of signal 61 from about 10Hz to 30Hz.

The master sync generator 50 supplies a signal 52 to controller 60.Output signals 61 and 62 are derived from this input signal 52, thusmaintaining a precise timing relationship among all of the signals inthe system.

As described in co-pending application Ser. No. 180,369, certainmodifications can be made to a standard video signal such that it can bedisplayed on a standard TV receiver or monitor, but cannot be recordedon a standard video tape recorder. The present invention applies theform of signal modification described in said co-pending applicationSer. No. 180,369 during the process of making a master for an opticalvideo disc. All discs produced from such a master can be played on astandard optical video disc players to produce a video output signalthat can be viewed on standard TV receivers and monitors but whichcannot be recorded on standard video tape recorders.

FIG. 2 shows the method for encoding an optical video disc to inhibitvideo tape recording in accordance with the present invention. Thefigure is similar to FIG. I except that the video and audio outputs 41and 42 respectively, of VTR 40 are not applied directly to signalprocessor 31 but, rather, they feed a video modification processor 70,as described in said copending application. A time code output 43 of VTR40 also feeds video modification processor 70. The video signal 41 ismodified by video modification processor 70 in accordance with apredetermined profile which is supplied at input 81 by a profilegenerator 80. Lines in individual fields of the video signal are addedan deleted such that the output video signal 71 from processor 70 cannotbe successfully recorded on a video tape recorder, although it can stillbe displayed on a standard TV receiver or monitor.

In addition to changing the number of lines in individual fields, thevideo modification processor 70 performs other modifications to thevideo signal to minimize any residual effects on standard TV receiversand monitors due to changing the number of lines in a field. The exactnature of the video modification processing varies from field to fieldin accordance with a predetermined profile. The profile signal at input81 in conjunction with the time code output 43 is used by the videomodification processor 70 to determine the exact processing for eachfield of the video signal 41. Audio output 72 is a delayed replica ofaudio input 42. The delay matches the delay inherent in processing thevideo signal from input 41 to output 71.

The modifications made to the video and audio signals 41 and 42 by thevideo modification processor 70 to produce the modified video and audiosignals 71 and 72 have no effect on the subsequent processing by theelectronics package 30. However, the functions of signal processor 31may be included in the video modification processor 70.

The signal 71 from the video modification processor 70 is recorded onthe master. All optical video discs made from this master thus willcontain the processed signal 71. When played back, this signal isreproduced and can be displayed on standard TV receivers and monitorsbut cannot be recorded by standard video tape recorders.

In practice, the process of making a master with the system of FIG. 2 issimilar to that of FIG. 1. A blank disc 13 is mounted on the turntable10. A source tape is mounted on VTR 40, the transport 23 is positionedin the vicinity of the outer edge of the blank disc 13 and profileinformation is loaded into profile generator 80. The motor start input63 to controller 60 is then activated to cause signal 61 to be suppliedto motor driver 12.

The VTR 40 is activated, and upon reaching an initial cue point thestart input 64 to controller 60 is activated to begin the recordingprocess. The video signal 4-, audio signal 42 and time code signal 43all feed into the video modification processor 70 from VTR 40. Thepredetermined profile signal 81 also feeds into video modificationprocessor 70. The modified video signal 71 and audio signal 72 then feedinto signal processor 31 from video modification processor 70. Fromthere, the recording process is as shown in FIG. 1.

While the present invention has been particularly shown and describedwith reference to preferred embodiments, it will be readily understood bthose of skill in the art that various changes and modifications may bemade without departing from the spirit and scope of the invention.

What is claimed is:
 1. A method of making an optical video disc toinhibit unauthorized recording of played back signals by conventionalvideo tape recorders but enable the display of a video picture fromthose played back signals on a television receiver, comprising the stepsof: generating a video signal from a source program; modifying the videosignal by increasing the time durations of horizontal line intervalsincluded in a first predetermined number of frames of said video signalfrom a standard horizontal line duration to a pre-established maximumtime duration and then decreasing said time durations from saidpre-established maximum to said standard and decreasing the timedurations of the horizontal line intervals included in a secondpredetermined number of frames of said video signal from said standardto a pre-established minimum time duration and then increasing said timedurations from said pre-established minimum to said standard; andrecording the modified video signal on a previously blank optical videodisc.
 2. A method according to claim 1, comprising the additional stepsof: rotating a blank optical video disc in response to a start signal;focussing a spot on the blank disc; moving the spot radially over thedisc; synchronizing the radial movement of the spot and the rotation ofthe disc; and using the spot to make selected pits in the surface of thedisc.
 3. A method according to claim 2, comprising the additional stepsof: conditioning the video signal for recording in accordance with thecharacteristics and standards for said optical video disc; and frequencymodulating a carrier with the modified video signal to form the signalto be recorded on the blank disc.
 4. A method of making an optical videodisc to inhibit unauthorized recording of played back signals byconventional video tape recorders but enable the display of a videopicture from those played back signals on a television receiver,comprising the steps of: generating a video signal from a sourceprogram; increasing above a standard number of horizontal line intervalsnormally included in a frame the number of horizontal line intervalsincluded in a first predetermined number of frames of said video signal;decreasing below said standard number the number of horizontal lineintervals included in a second predetermined number of frames of saidvideo signal; the rate at which the numbers of horizontal line intervalsare increased and decreased, the maximum and minimum numbers ofhorizontal line intervals in a frame to which said numbers of horizontalline intervals are increased and decreased, and the first and secondpredetermined numbers of frames containing the increased and decreasednumbers of horizontal line intervals all corresponding to a profilepattern representing changes with respect to time in the number ofhorizontal line intervals in a frame and having a positive portionrepresenting said first predetermined number of frames containing morethan said standard number of horizontal line intervals in each frame anda negative portion containing less than said standard number ofhorizontal line intervals in each frame; selectively changing saidprofile pattern and correspondingly changing at least one of thefollowing: (a) the rate at which the number of horizontal line intervalsin a frame change; (b) the maximum number of horizontal line intervalsincluded in a frame; (c) the minimum number of horizontal line intervalsincluded in a frame; (d) the first predetermined number of framescontaining more than said standard number of horizontal line intervals;and (e) the second predetermined number of frames containing less thansaid standard number of horizontal line intervals; and recording themodified video signal o a previously blank optical video disc.
 5. Amethod according to claim 4, comprising the additional steps of:rotating blank optical video disc in response to a start signal;focussing a laser to a spot on the blank disc; moving the laser radiallyover the disc; synchronizing the radial movement of the laser and therotation of the disc; and using the laser to make selected pits in thesurface of the disc.
 6. A method according to claim 5, comprising theadditional step of: conditioning the video signal for recording inaccordance with the characteristics and standards for said optical videodisc; and frequency modulating a carrier with the modified video signalto form the signal to be recorded on the blank disc.
 7. An apparatus formaking an optical video disc to inhibit unauthorized recording of playedback signals by conventional video tape recorders but enable the displayof a video picture from those played back signals on a televisionreceiver comprising: means for generating a video signal from a sourceprogram; video signal modifying means for modifying the video signalincluding line duration increasing means for increasing the timedurations of horizontal line intervals included in a first predeterminednumber of frames of the video signal from a standard horizontal lineduration to a preestablished maximum time duration and then decreasingsaid time durations from said pre-established maximum to said standard,and line duration decreasing means for decreasing the time durations ofthe horizontal line intervals included in a second predetermined numberof frames of the video signal from said standard to a pre-establishedminimum time duration and then increasing said time durations from saidpre-established minimum to said standard; and recording means forrecording the modified video signal on a previously blank optical videodisc.
 8. An apparatus according to claim 7, further comprising: rotationmeans for rotating a blank optical video disc on which a signal is to berecorded; drive means for driving said rotation means; laser means forrecording said signal to be recorded on said blank optical video disc bycreating pits in the surface of the video disc; laser drive means forproviding the signal to be recorded to said laser means; focus means forfocussing light from said laser means to a spot on said video disc;transport means for moving said laser means radially over the blankvideo disc; signal processor means for conditioning the modified videosignal in accordance with characteristics and standards of standardvideo disc players; and frequency modulation means for frequencymodulating a carrier with the conditioned, modified video signal andsupplying the frequency modulated carrier to said laser drive means. 9.An apparatus according to claim 8, further comprising: synchronizationmeans for synchronizing said means for generating a video signal andsaid drive means.
 10. An apparatus for making an optical video disc toinhibit unauthorized recording of played back video signals byconventional video tape recorders but enable the display of a videopicture from those played back video signals on a television receivercomprising: means for generating a video signal from a source program;video signal modifying means, including line interval increase means forincreasing above a standard number of horizontal line intervals normallyincluded in a frame the number of horizontal line intervals included ina first predetermined number of frames of the video signal, lineinterval decrease means for decreasing below said standard number thenumber of horizontal line intervals included in a second predeterminednumber of frames of the video signal, profile means for providing aprofile pattern representing changes with respect to time in the numberof horizontal line intervals in a frame, said profile pattern havingpositive portion representing said first predetermined number of framescontaining more than said standard number of horizontal line intervalsin each frame and a negative portion representing said secondpredetermined number of frames containing less than said standard numberof horizontal line intervals in each frame, means for selectivelychanging said profile pattern, means for applying said profile patternto said line interval increase and decrease means for changing at leastone of the following: (a) the rate at which the number of horizontalline intervals in a frame change, (b) the maximum number of horizontalline intervals included in a frame, (c) the minimum number of horizontalline intervals included in a frame, (d) the first predetermined numberof frames containing more than said standard number of horizontal lineintervals; and (e) the second predetermined number of frames containingless than said standard number of horizontal line intervals; andrecording means for recording the modified video signal on a previouslyblank video disc.
 11. An apparatus according to claim 10, furthercomprising: rotation means for rotating a blank video disc on which asignal is to be recorded; drive means for driving said rotation means;laser means for recording said signal to be recorded on said blankoptical video disc by creating pits in the surface of the video disc;laser drive means for providing the signal to be recorded to said lasermeans; focus means for focussing light from said laser means to a spoton said video disc; transport means for moving said laser means radiallyover the blank optical video disc; signal processor means forconditioning the modified video signal in accordance with standards andcharacteristics of standard video disc players; and frequency modulationmeans for frequency modulating a carrier with the conditioned, modifiedvideo signal and supplying the frequency modulated carrier to said laserdrive means.
 12. An apparatus according to claim 11, further comprising:synchronization means for synchronizing said means for generating avideo signal and said drive means.
 13. An apparatus for making anoptical video disc to inhibit unauthorized recording of played backvideo signals by conventional video tape recorders but enable thedisplay of a video picture from those played back video signals on atelevision receiver comprising: means for generating a video signalcorresponding to a source program; video signal modification means formodifying said video signal so as to permit said video signal to bedisplayed on a standard television receiver, but not recorded on astandard video tape recorder; variable profile generator means forfeeding a changeable profile signal pattern to said video signalmodification means to determine the patter of signal modification;signal processing means for conditioning the modified video signal inaccordance with standard optical video disc player parameters; andrecording means for recording the conditioned signal on a previouslyblank optical video disc.
 14. The apparatus of claim 13 wherein saidrecording means includes a laser for directing a laser beam onto saidoptical video disc, and means for modulating said laser beam with saidconditioned signal.
 15. The apparatus of claim 13 wherein said recordingmeans includes an electrode beam source for directing an electron beamonto said optical video disc, and means for modulating said electronbeam with said conditioned signal.
 16. The apparatus of claim 13 whereinsaid recording means includes a mechanical stylus for scribing saidoptical video disc, and means for controlling said stylus with saidconditioned signal.